Visual, instrumental, mycological and mycotoxicological characterization of wheat inoculated with and protected against Alternaria spp.

The aim of this work was to characterize visual properties, instrumentally measured colour properties, field fungi presence and Alternaria toxins levels in wheat samples grown under conditions aimed at inhibition and stimulation of wheat infection with fungi from the Alternaria genus. Experiment was carried out on the wheat treated by fungicide and wheat inoculated by Alternaria spp., while non treated wheat was used as a control. Statistically significant difference was observed between all three treatments using visual scale. Protected wheat samples were significantly different from other samples in terms of all measured colour parameters while inoculated and control wheat samples were significantly different in terms of lightness and dominant wavelength. Identification of field fungi in the all examined wheat samples showed that the dominant mycotoxigenic fungus was Alternaria spp., followed by Fusarium spp. The content of Alternaria toxins in samples of wheat hulls and dehulled kernels point out at higher concentrations of Alternaria toxins in hulls than in dehulled kernels.

Glufosinate-Ammonium Reduces Growth and Aflatoxin B1 Production by Aspergillus flavus

The herbicide glufosinate-ammonium (GA) [butanoic acid, 2-amino-4-(hydroxymethylphosphinyl)-ammonium salt] was tested at concentrations from 2 to 2,000 g GA per ml for activity against growth and aflatoxin B1 (AFB1) production by the mycotoxigenic fungus Aspergillus flavus Link:Fr. The highest concentration (2,000 μg GA per ml) reduced colony diameter of A. flavus strain AF13 by 80%. AFB1 production was inhibited by 90% at this concentration. Reduction in mycelial dry weight and AFB1 production in response to GA application ranged from 17.2 to 97.1% and from 39.1 to 90.1%, respectively. Of four concentrations tested, 2 μg GA per ml was weakly inhibitory. In the kernel screening assay, AFB1 production was inhibited 60 to 91% when kernels were preimmersed or immersed 5 days after incubation in 200 μg GA per ml. Both concentrations (2 and 200 μg GA per ml) reduced seed germination by 25 to 50%. Results indicate that GA has an inhibitory effect on growth and AFB1 production by A. flavus.

RELATION OF WEATHER VARIABLES TO INCIDENCE OF ZEARALENONE IN CORN IN SOUTHERN ONTARIO

Incidence of zearalenone was estimated according to frequency with which the mycotoxin was detected in corn (Zea mays L.) samples received for mycotoxin analyses at the Veterinary Services Laboratory, in Guelph, Ontario. Sampling periods were 1 Sept. to 31 May in 6 successive yr. Frequency of zearalenone was high in 1975–76, moderate in 1972–73, 1976–77 and 1977–78, and low in 1973–74 and 1974–75. Incidence of zearalenone-positive samples for each 104 ha grain corn was highest in a zone extending from the Bruce Peninsula to the Niagara region. Incidence of zearalenone-positive corn samples correlated strongly with rainfall for August, but only moderately or weakly with rainfall for July, September and October. Rain promoted zearalenone accumulation indirectly by favoring epidemic development in corn of the mycotoxigenic fungus Fusarium graminearum. Correlations between zearalenone frequencies and temperatures were weak. Persistent wetness in corn increased ear rot development and incidence of zearalenone.